Controls for heating burners



April 3, 1956 J. BASCI CONTROLS FOR HEATING BURNERS Original Filed Feb.20, 1951 2 Sheets-Sheet 1 "V 8 .1 5 i ll m .w 7

INVENTOR. JOS E PH BASCI ATTOEN April 1955 J. BASCI 2,740,863

CONTROLS FOR HEATING BURNERS Original Filed Feb. 20. 1951 2 Sheets-Sheet2 Q g. g

THEEMOSTAT JNVENTOR. JOSEPH BASCI AT TOP/VEY.

FLAME United States Patent CONTROLS FUR HEATING BURNERS Joseph Basel,iOOiilJlll, N. Y.

Original application February 2%], 1951, Serial No. 211,924, now PatentNo. 2,669,298, dated February 16, 1954. Divided and this applicationOctober 26, 1953, Serial No. 388,146

3 Claims. ((31.200-124) This invention relates to new and usefulimprovements in burner control systems and more particularly to animproved electronic safety control system for fluid or gas burners.

This application is a division of my application Serial Number 211,924,filed February 20, 1951, now U. S. Patent No. 2,669,298, grantedFebruary 16, 1954-.

In the operation of oil burners it is desirous to prevent an abnormaldischarge of fuel into the burner in the event of ignition failure orthe premature extinguishment of the flame; and in the operation of gasfired furnaces, ovens, etc., it is desirous to prevent the flow of gasthrough the main burner when the igniting medium is not functioning, orwhen the main burner flame is pre maturely extinguished. Further, it isdesirous to shut down the burner in the event of an open or shortcircuit in the control means therefor, a power failure, or the excessiveoverheating of the burner walls, and, in some instances, to reactuatethe igniting means in the event of flame failure.

One object of the invention is the provision of a highly efiicientcontrol system which is applicable to'both gas and oil burners and whichis effective to provide all of the desirous results listed above.

According to the invention there is provided a flame sensitive devicewhich in the case of an oil burner may be a photo-tube and which in thecase of a gas burner may be a flame rod, an electronic amplifiercontrolled by the flame sensitive device, control circuits operated bythe amplifier,.and a thermal switch actuated by a continuednon-operation of said control circuits.

Another object of the invention is the provision of control circuitryfor concomitantly reactuating the ignition means in the event of flameor ignition failure and for initiating an operation of the thermalswitch, which, however, does not operate if theflame is reignited.

Another object of the invention is the provsion of a highly etficientthermal switch capable of positive operation at the expiration of adefinite, predetermined time period and capable also of being resetmanually within a short time after operation thereof.

A controlling factor in the manufacture and marketing of control systemsof the type involved is cost, both original and maintenance.

A further object of the invention, therefore, is to construct the deviceof the invention in such manner that the same is capable of beingmanufactured economically, is capable of long life with a minimum ofmaintenance, and is adapted to rapid disassembly for adjustment andrepairs.

Other objects and features of the invention will become apparent fromthe following description when read in the light of the accompanyingdrawings of which:

Fig. 1 is a perspective view of the control unit of the invention incondition for mounting;

Fig. 2 is an exploded perspective view of the several component parts ofthe unit;

Fig. 3 is a perspective view of the unit that'illustrates the means forsecuring two of the casing components thereof together;

Fig. 4 is a sectional view on line 44 of Fig. l, with many non-essentialdetails left out;

Fig. 5 is a detached side elevational view of the thermal switch of theinvention, said switch being shown in mounted condition in Fig. 2;

Fig. 6 is a detached edge view of said switch;

Fig. 7 is a detached elevational view of the opposite side of theswitch;

Fig. 8 is a fragmentary, enlarged sectional view of the switch, and,

Fig. 9 is the wiring diagram of the invention.

Referring first to the wiring diagram of Fig. 9, the circuit illustratedtherein is primarily adapted to an oil burner but is readily adapted foruse with a gas burner. As shown, the circuit includes an ordinary threewire thermostat 15, a high limit control unit 16, the burner motor 17,the burner ignition unit 18, a transformer 20 having its primary coil 21connected to A. C. supply and having a pair of secondary coils 22 and23, a pair of relays KY1 and KY2, a thermal switch 24, and electronicamplifier 25, preferably a dual triode such as a l2SN7, and a photo-tube26 situated adjacent the burner flame and controlling said amplifier.For rotary pottype oil burners, the photo-tube 26 is replaced by a flamerod 27. For gas burners with pilot flame control, the flame rod 27 isused on the pilot flame, the main gas valve replaces the motor 17, andthe ignition circuits are eliminated.

The one side of motor 17 and ignition unit is are connected by a lead 28to one supply line 36. The other side of the motor, however, isconnected by leads 31 and 32 through a normally opened contact 33 ofrelay RYl to the other supply line 34, and ignition unit 18 is connectedwith lead 31 by leads 35 and 36 through normally closed contacts 37 ofrelay RY2. Thus a normally open contact is provided in the motorcircuit, and, said open contact along with a normally closed contactcontrol operation of the ignition unit. Motor control relay RYI isconnected by a lead 38 with one side of secondary coil 23 and by a lead46 with a normally open contact 41 of the thermostat 15. Closure ofcontact 41 completes a circuit through a second contact 42 of thethermostat, lead 43, normally closed contacts 44 of relay RYZ, lead 45,thermal switch 24 and lead 46 to the other side of transformer coil 23.

The construction thus far described is such that operation of thermostatl5 energizes relay RYI which closes contacts 33 and initiates operationof ignition unit 18- and motor 17.

Relay RYI is also provided with normally open contacts 47 which areconnected by an extension 48 of lead 4-6 with one side of coil 23 and bya lead at) to the heater filament 51 of amplifier 25. By means of asurge limiting resistor 52 and the lead 38, the other side of the heaterfilament is connected back to coil 23. Thus, onenergization of relay RYa circuit is completed to heater 51 through contacts 47 and surgelimiting resistor 52.

Completing a circuit to a heater filament, normally occasions a currentsurge equal to six or seven times the normal current drawn by theheater, which greatly reduces the life of the tube. By inserting theresistor 52 in the circuit this current surge is limited toapproximately twice the normal value which not only lengthens the lifeof the tube, but also lessens the standby power requirenients andeliminates the need for a special heater winding on transformer 28. Thisarrangement, of-course, is highly advantageous in that it lowers boththe initial and maintenance costs of the device.

Amplifier 25 may be connected in any desired manner but preferably isconnected as shown in Fig. 9. Forconvenience, the two halves ofamplifier 25 will be referred to as tubes A and B, the left hand one inFig. 9 being tube A. As shown the cathode 55 of tube A is connected to atap of coil 22. The grid 58 of tube A is connected by a lead 60 througha large resistor 61 to the anode 62 of photo-tube 26. A large resistor63 and a capacitor 64 are connected across leads 56 and 60. Resistances63 and 61 and condenser 64 must be properly proportioned to provideproper bias for tube A and to provide a time constant of the propervalue to maintain the bias during the negative swings of the coil 22.

Suggested values for these resistors and for the other circuitcomponents will be listed at the end of the description. The anode 65 oftube A is directly coupled to the grid 58 of tube B and through a largeresistor 66 and lead 67 to the other end of transformer coil A smallerresistor 68 also connects said anode to the cathode of tube B. The anodeof tube B is connected through the coil of relay RYZ and a lead 69 tolead 67 and transformer coil 22. By means of a lead 70 and a capacitor71, the cathode of tube B which is connected to the tap of coil 22, iscoupled back to the anode 62 of photo-tube 26.

The operation is as follows: Assuming that a flame is causing photo-tube26 to conduct, the latter rectifies the A. C. voltages applied throughlead 70 from the tap of coil 22. Thus, a pulsating D. C. bias is appliedto tube A causing the latter to become non-conductive. The charge oncondenser 64 maintains the bias at a level sufi'icient for cutoff duringthe negative swings of coil 22. When tube A is cut off, the potential ofits plate rises causing an increased current flow in tube B. Thisenergizes relay RYZ. In order to maintain relay KY2 energized during thenegative swings of coil 22, a large capacitor 72 is connected across thecoil thereof.

The construction of the amplifier is such that when photo-tube 26 isconducting, or rectifying, the relay RY 2 is energized, but when thephoto-tube becomes non-rectifying the cathode to grid connection of tubeA is opened and the relay is deenergized.

It will be remembered that as described above, an operation ofthermostat effects energization of motor starting relay RY1 whichthrough the contacts associated therewith closed the motor and ignitioncircuits through a thermal switch and also closes a circuit for theheater of amplifier 25. Normally, closure of the motor and ignitioncircuits effects lighting of the flame in the burner, which throughphoto-tube 26 and amplifier results in energization of relay RYZ. Thisopens the normally closed contacts 37 and 44 of said relay which openthe ignition unit circuit and the circuit for relay RY1 through thermalswitch 24 respectively. However, normally open contacts 75 of relay RY2are closed and complete circuit for relay RYl which does not includethermal switch 24.

This circuit includes the lead which is also connected to contact 44, alead 76, closed contacts 77 of energized relay KY1, a lead 78, a commoncontact 80 of thermostat 15, contact 41 of the latter, lead 40, relayRY1, lead 38, transformer coil 23, leads 46 and 48, closed contacts 47of relay RYl, lead and a lead 81 connected back to contacts 75.

The construction is such that immediately following a successfuloperation of ignition unit 18 under control of thermostat 15, photo-tube26 and amplifier 25 effect both the inactuation of said ignition unitand also the shunting of the thermal switch 24 so that the latter doesnot heat up sufiiciently to open the circuit and turn off motor 17.

Thermal switch 24 preferably is of the unique construction to bedescribed hereinafter but may be of any type capable of openingpositively in approximately 50 seconds due to the heat provided byapproximately one watt of power, and capable also of being resetmanually within a short period of time. 7

Thus, if the ignition unit 18 fails to ignite a flame within thepredetermined period of approximately 50 seconds the thermal switch 24opens and prevents the further pumping of fuel into the burner bydeenergizing relay RY1. Further, if the flame should be extinguishedprematurely, the photo-tube 26 becomes non-rectifying and relay KY2 isdeenergized, bringing ignition unit 18 and thermal switch 24 back intothe circuit. This, of course, results either in a successful operationof the ignition unit 18 or in the opening of thermal switch 2 4. Tubefailures and short or open circuits in either relay RY2 or RY1 alsoresult in opening of thermal switch 24, since the shunt circuit forthermal switch 28 includes contacts 75 and 47 in series with each other.Thus, accidental closure of either contacts 75 or 47 is not sufiicientto short-circuit thermal switch 24, but rather both contacts 75 and 47must be simultaneously closed to establish a bypass or short-circuit forthermal switch 24.

It is believed evident that the opening of thermostat 15 conditions thedevice for the next operation.

It is desired, that thermal switch 24 open in the event relay RYZremains energized after thermostat 15 is opened, for example, when highinfra-red emission occurs due to overheated burner walls. This isaccomplished by a circuit which includes said switch, lead 46,transformer coil 23, resistor 52, heater 51, leads 50 and 81, closedcontacts 75 of energized relay RY2 and lead 45.

The thermal switch of the invention is illustrated in detail in Figs.5-8 and includes a plate 85 having a shelf 86 bent off therefrom at oneend and a shelf 87 at the other end. A large opening 88 in plate 85extends into shelf 87 so that the latter resembles a pair of earsinterconnected by a crosspiece. Shelves 86 and 87 are interconnected bybolts 90 which extend through sleeves 91 positioned between the shelvesand which are provided with nuts 92 for securing the unit in place.Riveted to plate 85 between shelves 86 and 87 and spanning the portionof opening 88 adjacent shelf 87 is a plate 93 of an insulative materialsuch as Bakelite. A tail 94 of plate 93 projects beyond shelf 87 and hassecured thereto a pair of terminals 95 for the leads 46 and 45, 76 ofthe wiring diagram of Fig. 9. Secured in a hole in plate 93 andextending between the shelves 86 and 87 is a hollow stem 96 of brass orother conductive material, said stem having wound thereon a heating coil97 which is insulated therefrom by a coating 98 of high temperatureinsulation. One end of the coil, however, is soldered to an annularflange or collar 100 of the stem near the free end of the latter. Theother end of the coil is connected by a lead 101 with one of theterminals 95. Mounted within stem 96 but fixed against rotation by alayer of solder 102 fixing it to the stem is a tubular pivot shaft 103for a pinion 104. At the free end of stem 96 the end of shaft 103 isflared out at 105 and abuts a bearing washer 106 positioned between saidflare and an annular collar 107 of said stem. A bearing washer 108 isalso provided between pinion 104 and the fixed end of stem 96.

It is to be mentioned that solder 102 may be of any commerciallyavailable type which will melt and free shaft 103 from stem 96 inapproximately 50 seconds due to the heat generated by coil 97 with aboutone watt of power.

Cooperating with pinion 104 is a pawl 110 of beryllium copper or thelike which is connected by a lead 111 with the terminal 95 to which theheater coil is not connected. Pawl 110 is secured to the flattened endof a rod 112 of Bakelite or the like which is slidably mounted in holesin shelf 86 and in a shelf 113 at the edge of opening 88. A pin 114projects through rod 112 and into a slot 115 in plate 85, thatextendslongitudinally of the rod and limits the amount of longitudinalmovement thereof. Slot 115 also prevents rotative or chatteringmovements of rod 112. A spring 116 is wound on rod 112 and acts betweenshelf 113 and pin 114 to move the rod in a direction to rotate pinion104 counterclockwise in Fig. 7.

The construction is such that normally solder 102 is effective toprevent rotation of pinion 104 and a circuit is completed from oneterminal 95 to the other through lead 101, coil 97, stem 96, solder 102,shaft 103, pinion 104, pawl 110 and lead 111. However, if solder 102should be melted by coil 97, the pinion 104 is rotated by pawl 110 whichmoves out of contact therewith to the dot-dash position of Fig. 7 andthe switch is opened.

To reset the switch all that is required is to allow a few moments forthe solder 102 to reharden, and to push rod 112 back to its initialposition, the pawl 110 readily springing to clear the upper portion ofthe pinion.

For convenience of installing and servicing the control device of theinvention, the same is assembled in unitary form as shown in Figs. 14.The relays RYl and RY2, transformer 20, thermal switch 24 and amplifier25 are mounted on one face of a rectangular box like chassis 117 whichincludes two main plates 118 and 120 each having a side wall 121 and anend wall 122 or 123 bent off therefrom. The side walls 121 and the endwalls 122 and 123 are, of course, oppositively located. Secured to plate120 and to end wall 123 of plate 118 are the pivot supports 124 of ahinge which also includes a removable pivot pine 125. Thus plates 118and 120 with their oppositively disposed walls 121 and 122 or 123 form abox which is openable about hinge 124, 125 but which may be locked inclosed condition by the engagement of a wide head screw 126 in an openend slot 127 in end wall 122. Screw 126 is threaded into a bracket 128secured to plate 118, and when drawn up, effectively prevents swingingmovement of plate 120 about pivot pin 125.

The circuitory associated with relays RYI and RY2, transformer 20,thermal switch 24 and amplifier 25 is secured to the rear face of plate118 and is covered and protected by an insulative plate 129 bolted tothe bracket 128 and to another bracket 130. Secured to the forward faceof plate 120 are a pair of insulative blocks 131 each having thereon aplurality of screw terminals to which the appropriate leads of a cable132 extending from the circuit elements on plate 118, are connected. Theend wall 122 and side wall 121 of plate 120 are provided with suitablecapped openings 133 through which cables 134 are extended to connect theunit with a source of supply, a thermostat, a burner motor, etc.

Plate 120 is provided with suitable holes 135 by which the same may bemounted on a convenient wall or the like. The elements mounted on plate118 are covered and protected by a deep sheet metal cover 136 whichembraces the plate 118 and slight portions of the side walls 121 and endwalls 122 and 123. Cover 136 is secured in place by a pair of screws 137which are threaded into the end Walls 122 and 123 and engage in open endslots 128 in the edge of the cover. in order to accommodate the resetrod 112 of thermal switch 24 a hole 140 is provided in cover 136.

It will be seen, therefore, that in the event thermal switch 24 operatesas described above, the reset rod 112 projects to the dot-dash lineposition of Fig. 1 through the cover hole 140, and can be reset merelyby pushing it to the full line position illustrated. And, if it isdesired to service the elements mounted exteriorly of chassis 117, allthat is required is to loosen screws 137 and remove cover 136. Further,to service the interior of chassis 117, the latter may be swung open onhinge 124, 125 by loosening screw 126 or may be completely disassembledby removing pivot pin 125.

There has been provided, therefore, a highly efiicient control unit forthe purpose set forth that is not only economical in initial cost butalso in installation and main tenance.

Suggested values for the several circuit constants are as follows:

Resistor 61 -r l8-20 megohms. Resistor 63 18-2O megohms. Resistor 66100,000 ohms. Resistor 68 15,00022,000 ohms. Resistor 52 40-50 ohms.Condenser 64 .Ol mfd.

Condenser 71 .002 mfd.

Condenser 72 4 mfd.

Amplifier 25 12SN7;

Phototube 26 922 (vacuum). Transformer coil 22 225 volts, center tap 200volts. Transformer coil 23 24 volts.

While there has been described a preferred embodiment of the inventionit is to be understood that many changes in details of the constructioncan be made without departing from the spirit of theinven'tion.

I claim:

1. A thermal switch comprising a rigid frame, an insulative manual resetrod endwise slidably mounted in the frame, spring means tensioning saidrod in one endwise direction, an insulative panel secured to said frame,terminal lugs mounted on said insulative panel for placing the switch inan electric circuit a conductive stem projecting through and secured insaid panel, a second conductive stem located within the first, a layerof low temperature melting solder fixing said stems together andconecting them electrically, a conductive pinion fixed on one end of thesecond stem, a conductive spring pawl electrically connected to one ofsaid terminal lugs secured to said rod and engaging said pinion to makeelectrical. contact therewith and to prevent endwise movement of the rodby said spring, a heating coil wound on the outer stern and electricallyinsulated therefrom except for one end, said one end making electricalcontact with said outer stem, the other end of said heating coil beingelectrically connected to the other of said terminal lugs said coilbeing adapted to melt said solder in a predetermined amount of time toallow said pawl to rotate said pinion and move out of contact therewith.

2. A thermal switch comprising a rigid frame plate having ears bent oiftherefrom and an opening therein, an insulative manual reset rod endwiseslidably mounted in said ears, a pin projecting through the rod, a slotin said plate through which said pin projects to guide the rod and limitthe amount of endwise movement thereof, a spring acting against said pinto move the rod in an endwise direction, an insulative panel mounted insaid opening, a conductive stem projecting through and secured in saidpanel, a second conductive stern located within the first, a layer oflow temperature melting solder fixing said stems together and connectingthem electrically, a conductive pinion fixed on one end of the secondstem, a conductive spring pawl forming part of the electrical conductivepath through the switch in operation secured to said rod and engagingsaid pinion to make electrical contact with said pinion and to preventendwise movement of the rod by said spring, a heating coil forming partof the electrical conductive path through the switch in operation woundon the outer stern and electrically insulated therefrom except for oneend, said coil being adapted when the current passing through the switchexceeds a predetermined amperage to melt said solder in a predeterminedamount of time to allow said pawl to rotate said pinion and move out ofcontact therewith, and terminal lugs to which said pawl and the otherend of the heating coil are connected electrically.

3. A thermal switch comprising a rigid frame plate having ears bent otr'therefrom and an opening therein, an insulative manual reset rod endwiseslidably mounted in said ears, a pin projecting through the rod, a slotin said plate through which said pin projects to guide the rod and limitthe amount of endwise movement thereof, a

amaees 7 spring acting against said pin to move the rod in an endwisedirection, an insulative panel mounted in said opening, a conductivestem projecting through and securedin said panel, a pair ofannularcollars on said stern, one near and the other at the free endthereof, a second conductive stem located within the first, a flared endon the second stem adjacent the said end collar, a bearing Washerbetween said flared end and said end collar, 2. layer of low temperaturemelting solder fixing the two stems together and connecting themelectrically, a conductive pinion fixed on the other end of the secondstem, a bearing washer between said pinion and the end of the outerstern, a con ductive spring pawl secured to said rod and engaging saidpinion to prevent endwise movement of the rod by said spring and to makeelectrical contact with said pinion, a heating coil wound on the outerstem and electrically insulated therefrom, one end of said coil beingconnected to the collar near to the face end of said stem, said coil 8being adapted when electric current passes therethru to melt said solderin-a predetermined amount of time to allow said pawl to rotate saidpinion and move out of contact therewith, and terminal lugs to whichsaid pawl and the other end of the heating coil are electricallyconnected.

References Cited in the file of this patent UNITED STATES PATENTS1,569,815 Kirkland Jan. 12, 1926 1,678,800 Baker July 31, 1928 1,752,514Van Valkenburg Apr. 1, 1930 1,966,926 Darnell et al July 17, 19341,978,713 Knight Oct. 30, 1934 2,276,085 Pearson Mar. 10, 1942 2,532,265Zickrick Nov. 28, 1950 2,597,068 Cobb May 20, 1952

